Exercise mitigates many cardiovascular risk factors associated with atrial fibrillation. Endurance training has been associated with atrial structural changes which can increase the risk for atrial fibrillation. The dose of exercise training required for these changes is uncertain. We sought to evaluate the impact of exercise on left atrial (LA) mechanical and electrical function in healthy, sedentary, middle-aged adults.

LA volume, Vo2 max, and left ventricular end-diastolic volume increased in the exercise group (15%, 17%, and 16%, respectively) with no change in control (P<0.0001). LA active emptying decreased post-exercise versus controls (5%; P=0.03). No significant changes in filtered P-wave duration or root mean square voltage of the last 20 ms occurred after exercise training. LA and left ventricular volumes remained below Masters athletes. The athletes had longer filtered P-wave duration but no difference in the frequency of atrial arrhythmia.

Conclusions:

Changes in LA structure, LA mechanical function, and left ventricular remodeling occurred after 10 months of exercise but without significant change in atrial electrical activity. A longer duration of training may be required to induce electrical changes thought to cause atrial fibrillation in middle-aged endurance athletes.

Although cardiac resynchronization therapy (CRT) is beneficial in heart failure patients with left bundle branch block, 30% of these patients do not respond to the therapy. Identifying these patients before implantation of the device is one of the current challenges in clinical cardiology.

Methods:

We verified the diagnostic contribution and an optimized computerized approach to measuring ventricular electrical activation delay (VED) from body surface 12-lead ECGs. We applied the method to ECGs acquired before implantation (baseline) in the MADIT-CRT trial (Multicenter Automatic Defibrillator Implantation-Cardiac Resynchronization Therapy). VED values were dichotomized using its quartiles, and we tested the association of VED values with the MADIT-CRT primary end point of heart failure or death. Multivariate Cox proportional models were used to estimate the risk of study end points. In addition, the association between VED values and hemodynamic changes after CRT-D implantation was examined using 1-year follow-up echocardiograms.

RESULTS:

Our results showed that left bundle branch block patients with baseline VED <31.2 ms had a 35% risk of MADIT-CRT end points, whereas patients with VED ≥31.2 ms had a 14% risk (P<0.001). The hazard ratio for predicting primary end points in patients with low VED was 2.34 (95% confidence interval, 1.53–3.57; P<0.001). Higher VED values were also associated with beneficial hemodynamic changes. These strong VED associations were not found in the right bundle branch block and intraventricular conduction delay cohorts of the MADIT-CRT trial.

Conclusions:

Left bundle branch block patients with a high baseline VED value benefited most from CRT, whereas left bundle branch block patients with low VED did not show CRT benefits.

Western blot and voltage-clamping analyses of cells expressing E90K-, G294V-, R791W-, and R1005W-Kv11.1 channels demonstrated these variants express and generate peak Kv11.1 current levels similar to cells expressing wild-type-Kv11.1 channels, but R791W- and R1005W-Kv11.1 channels accelerated deactivation and activation gating, respectively. Electronic health records of patients with the sudden infant death syndrome–linked KCNH2 variants showed that the patients had median heart rate–corrected QT intervals <480 ms and none had been diagnosed with long-QT syndrome or experienced cardiac arrest. Simulating the impact of dysfunctional gating variants predicted that they have little impact on ventricular action potential duration.

Conclusions:

We conclude that these rare Kv11.1 missense variants are not long-QT syndrome subtype 2–causative variants and therefore do not represent the pathogenic substrate for sudden infant death syndrome in the variant-positive infants.

Hot balloon ablation (HBA) and cryoballoon ablation (CBA) were developed to simplify ablation for atrial fibrillation. Because the lesion characteristics and efficacy of these balloon modalities have not been clarified, we compared lesion characteristics and outcomes of HBA and CBA.

Patients’ clinical characteristics, including age, sex, body mass index, atrial fibrillation subtype, CHA2DS2-VASc score, and left atrial dimension, were similar between the 2 groups. Touch-up radiofrequency ablation was required for residual/dormant pulmonary vein conduction in 52% of the patients with HBA versus 24% of the patients with CBA (P=0.02) and often in the anterior aspect of the left superior pulmonary vein after HBA (41%) versus the inferior aspect of the inferior pulmonary veins after CBA (22%). HBA lesions were smaller than CBA lesions (23.8±7.9 versus 33.5±14.5 cm2; P=0.0007). Similar results were observed when lesions in each pulmonary vein were compared between groups. Twentyfour hours after the procedure, serum levels of the cardiac biomarkers, including troponin-T, creatine kinase, and creatine kinase-MB, were higher in the HBA group than in the CBA group. Atrial fibrillation recurrence did not differ between the groups within 6 (3% versus 11%; P=0.36) or 12 months (16% versus 16%; P=1.00).

Conclusions:

Although HBA lesions appear to be smaller than CBA lesions, middle-term outcomes are not statistically different between these balloon modalities.

Sympathetic denervation exerts protective effects against ventricular arrhythmias (VAs) induced by acute myocardial infarction. The results of a previous study indicated that the distal part of the ligament of Marshall (LOMLSPV) might be a sympathetic conduit between the left stellate ganglion (LSG) and the ventricles. The present study was designed to compare the effects between LSG and LOMLSPV ablation on ischemia-induced VAs.

Methods:

Twenty-nine dogs were randomly divided into sham ablation group (group 1, n=9), LOMLSPV ablation group (group 2, n=10), and LSG ablation group (group 3, n=10). Ablation was performed before occlusion of the left anterior coronary artery. Changes in the heart rate variability, serum norepinephrine, ventricular effective refractory period, and blood pressure induced by LSG stimulation were observed, and the occurrence of VAs was recorded. Immunostaining examinations of LOMLSPV were performed in dogs without ablation.

The prevalence of atrial fibrillation (AF) in active astronauts is 5%, similar to the general population but at a younger age. Risk factors for AF include left atrial enlargement, increased number of premature atrial complexes, and certain parameters on signal-averaged electrocardiography, such as P-wave duration, root mean square voltage for the terminal 20 ms of the signal-averaged P wave, and P-wave amplitude. We aimed to evaluate changes in atrial structure, supraventricular beats, and atrial electrophysiology to determine whether spaceflight could increase the risk of AF.

Methods:

Thirteen astronauts underwent cardiac magnetic resonance imaging to assess atrial structure and function before and after 6 months in space and high-resolution Holter monitoring for multiple 48-hour time periods before flight, during flight, and on landing day.

RESULTS:

Left atrial volume transiently increased after 6 months in space (12±18 mL; P=0.03) without changing atrial function. Right atrial size remained unchanged. No changes in supraventricular beats were noted. One astronaut had a large increase in supraventricular ectopic beats but none developed AF. Filtered P-wave duration did not change over time, but root mean square voltage for the terminal 20 ms decreased on all fight days except landing day. No changes in P-wave amplitude were seen in leads II or V1 except landing day for lead V1.

Conclusions:

Six months of spaceflight may be sufficient to cause transient changes in left atrial structure and atrial electrophysiology that increase the risk of AF. However, there was no definite evidence of increased supraventricular arrhythmias and no identified episodes of AF.

Severe PV stenosis was diagnosed in 52 patients (0.5%). This involved mostly the left superior PV (51% of severely stenosed veins). Percutaneous interventions were performed in 43 patients, and complications occurred in 5: 3 PV ruptures, 1 stroke, and 1 phrenic injury. Over a median follow-up of 25 months, 41 (79%) patients remained arrhythmia free. Repeat ablation was performed in 15 patients (7 from the main series and 8 from prior ablation at other institutions); of whom 10 had PV stents in place. Conduction recovery was noted in all but 2 of the stenosed or stented PVs, and areas with recovery were targeted with antral ablation. Lasso entrapment within stents occurred in 2 patients but eventually freed without complications. After redo ablation, preplanned stenting was performed in 3 patients and computed tomographic scans showed progression of concomitant stenoses in 1 patient (moderate to severe). No procedure-related deaths occurred.

Conclusions:

The incidence of severe PV stenosis is low but remains associated with significant morbidity. In patients with recurrent arrhythmia, conduction recovery at the stenosed or stented veins is common. Care must be taken to ablate antrally to avoid stenosis progression. In patients with prior PV stents, we suggest to avoid using Lasso.

Obesity, characterized by systemic low-grade inflammation, is considered a well-known risk for atrial fibrillation. In fact, IL-10 (interleukin 10), which is a potent anti-inflammatory cytokine, has been reported to decrease in obese and diabetic patients. We tested the hypotheses forwarding that genetic deletion of IL-10 exacerbates high-fat diet (HFD)–induced obesity-caused atrial inflammation, lipidosis, fibrosis, and fibrillation and that IL-10 therapy inhibits this pathology.

Methods:

Eight- to 10-week-old male CL57/B6 (wild-type) mice and IL-10 knockout mice were divided into a 12-week HFD group and a 12-week normal-fat diet (NFD) group, respectively. In addition, the effect of IL-10 administration was also investigated.

RESULTS:

HFD-induced obesity for 12 weeks significantly depressed serum levels of IL-10 but were found to increase several proinflammatory cytokines in wild-type mice. Adverse atrial remodeling, including atrial inflammation, lipidosis, and fibrosis, was induced in both wild-type and IL-10 knockout mice by HFD. Vulnerability to atrial fibrillation was also significantly enhanced by HFD. With regard to epicardial and pericardial adipose tissue, the total amount of epicardial adipose tissue+pericardial adipose tissue volume was increased by HFD. Besides, proinflammatory and profibrotic cytokines of epicardial adipose tissue+pericardial adipose tissue were also upregulated. In contrast, the protein level of adiponectin was downregulated by HFD. These HFD-induced obesity-caused adverse effects were further exaggerated in IL-10 knockout mice in comparison to wild-type mice. Systemic IL-10 administration markedly ameliorated HFD-induced obesity-caused left atrial remodeling and vulnerability to atrial fibrillation, in addition to improving the quality of epicardial adipose tissue+pericardial adipose tissue.

Inverse electrocardiographic mapping reconstructs cardiac electrical activity from recorded body surface potentials. This noninvasive technique has been used to identify potential ablation targets. Despite this, there has been little systematic evaluation of its reliability.

Mean correlation coefficients for reconstructed epicardial potential distributions ranged from 0.60±0.08 to 0.64±0.07 across all methods. Epicardial electrograms were recovered with reasonable fidelity at 50% of sites (median correlation coefficient, 0.69–0.72), but variation was substantial. General activation spread was reproduced (median correlation coefficient, 0.72–0.78 for activation time maps after spatio-temporal smoothing). Epicardial foci were identified with a median location error 16 mm (interquartile range, 9–29 mm). Inverse mapping with meshless method of fundamental solutions was better than with finite/boundary element methods, and the latter were not improved by inclusion of inhomogeneous torso electrical properties.

Conclusions:

Inverse potential mapping provides useful information on the origin and spread of epicardial activation. However the spatio-temporal variability of recovered electrograms limit resolution and must constrain the accuracy with which arrhythmia circuits can be identified independently using this approach.

The outcomes from pulmonary vein isolation (PVI) for atrial fibrillation (AF) are suboptimal, but the benefits of additional lesion sets remain unproven. Recent studies propose ablation of AF drivers improves outcomes over PVI, yet with conflicting reports in the literature. We undertook a systematic literature review and meta-analysis to determine outcomes from ablation of AF drivers in addition to PVI or as a stand-alone procedure.

Methods:

Database search was done using the terms atrial fibrillation and ablation or catheter ablation and driver or rotor or focal impulse or FIRM (Focal Impulse and Rotor Modulation). We pooled data using random effects model and assessed heterogeneity with I2 statistic.

Results:

Seventeen studies met inclusion criteria, in a cohort size of 3294 patients. Adding AF driver ablation to PVI reported freedom from AF of 72.5% (confidence interval [CI], 62.1%–81.8%; P<0.01) and from all arrhythmias of 57.8% (CI, 47.5%–67.7%; P<0.01). AF driver ablation when added to PVI or as stand-alone procedure compared with controls produced an odds ratio of 3.1 (CI, 1.3–7.7; P=0.02) for freedom from AF and an odds ratio of 1.8 (CI, 1.2–2.7; P<0.01) for freedom from all arrhythmias in 4 controlled studies. AF termination rate was 40.5% (CI, 30.6%–50.9%) and predicted favorable outcome from ablation(P<0.05).

Conclusions:

In controlled studies, the addition of AF driver ablation to PVI supports the possible benefit of a combined approach of AF driver ablation and PVI in improving single-procedure freedom from all arrhythmias. However, most studies are uncontrolled and are limited by substantial heterogeneity in outcomes. Large multicenter randomized trials are needed to precisely define the benefits of adding driver ablation to PVI.

Data on predictors of long-term clinical outcomes after catheter ablation of atrial fibrillation (AF) are limited. We sought to assess the association of baseline covariates with clinical outcomes in the 750 patients with drug-refractory paroxysmal AF enrolled in FIRE AND ICE.

Methods:

In a 2-part analysis, univariate and multivariable Cox regression models were first used to identify baseline patient characteristics predictive of catheter ablation efficacy determined by the clinical end points of (1) atrial arrhythmia recurrence (primary efficacy failure), (2) cardiovascular rehospitalization, and (3) repeat ablation. Propensity score stratification methods were then used to account for differences in baseline characteristics between sexes.

After catheter ablation of paroxysmal AF, female sex was associated with an almost 40% increase in the risks of primary efficacy failure and cardiovascular rehospitalization. Primary efficacy failure was also adversely impacted by a history of direct current cardioversion, whereas hypertension had a negative impact on cardiovascular rehospitalization. History of AF was the only predictor of repeat ablation.

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Although treatment options for AF exist, many patients cannot be maintained in normal sinus rhythm. Amiodarone is an effective medication for AF but has limited clinical utility because of off-target tissue toxicity.

Methods:

Here, we use a pig model of AF to test the efficacy of an amiodarone-containing polyethylene glycol–based hydrogel. The gel is placed directly on the atrial epicardium through the pericardial space in a minimally invasive procedure using a specially designed catheter.

RESULTS:

Implantation of amiodarone-containing gel significantly reduced the duration of sustained AF at 21 and 28 days; inducibility of AF was reduced 14 and 21 days post-delivery. Off-target organ drug levels in the liver, lungs, thyroid, and fat were significantly reduced in animals treated with epicardial amiodarone gel compared with systemic controls in small-animal distribution studies.

Conclusions:

The pericardium is an underutilized therapeutic site and may be a new treatment strategy for AF and other cardiovascular diseases.

First, we used the cardiovascular computational model CircAdapt to characterize the isolated effect of intrinsic interventricular and intraventricular activation on CRT response (LVdP/dtmax). Simulated LVdP/dtmax (range: 1.3%–26.5%) increased considerably with increasing interventricular dyssynchrony. In contrast, the isolated effect of intraventricular dyssynchrony in either the LV or right ventricle was limited (LVdP/dtmax range: 12.3%–18.3% and 14.1%–15.7%, respectively). Effects of activation during biventricular pacing on LVdP/dtmax were small. Second, electrocardiographic imaging–derived activation characteristics of 51 CRT candidates were used to personalize ventricular activation in CircAdapt. The individualized models were subsequently used to assess the accuracy of LVdP/dtmax prediction based on the electrical data. The model-predicted LVdP/dtmax was close to the actual value in patients with left bundle branch block (measured–simulated: 2.7±9.0%) when only intrinsic interventricular dyssynchrony was personalized. Among patients without left bundle branch block, LVdP/dtmax was systematically overpredicted by CircAdapt (measured–simulated: 9.2±7.1%). Adding intraventricular activation to the model did not improve the accuracy of the response prediction.

Conclusions:

Computer simulations revealed that intrinsic interventricular dyssynchrony is the dominant component of the electrical substrate driving the response to CRT. Intrinsic intraventricular dyssynchrony and any dyssynchrony during biventricular pacing play a minor role in this respect. This may facilitate patient-specific modeling for prediction of CRT response.

This study was designed to estimate the costs of index hospitalizations after cardiac arrest in the United States.

Methods and Results:

We used the US Nationwide Inpatient Sample (2003–2012) to identify patients with cardiac arrest. Log transformation of inflation-adjusted cost was determined for care to patient outcomes. Overall, an estimated 1 387 396 patients were hospitalized after cardiac arrest. The mean age of the cohort was 66 years, 45% were women, and the majority were white. Inpatient procedures included coronary angiography (15%), percutaneous coronary intervention (7%), intra-aortic balloon pump (4.4%), therapeutic hypothermia (1.1%), and mechanical circulatory support (0.1%). The rates of therapeutic hypothermia increased from zero in 2003 to 2.7% in 2012 (P<0.001). Both hospital charges and inflation-adjusted cost increased linearly over time. In a multivariate analysis, predictors of inflation-adjusted cost included large hospital size, urban teaching hospital, and length of stay. Among comorbidities, atrial fibrillation or fluid and electrolytes imbalance was most associated with cost. Among selected interventions, the cost was significantly increased with automatic implantable cardioverter defibrillators (odds ratio, 1.83; P<0.001), intra-aortic balloon pump (odds ratio, 1.50; P<0.001), hypothermia (odds ratio, 1.28; P<0.001), and extracorporeal membrane oxygenation (odds ratio, 2.38; P<0.001).

Conclusions:

In the period between 2003 and 2012, postcardiac arrest hospitalizations resulted in a steady rise in associated health care cost, likely related to increased length of stay, medical procedures, and systems of care. Although targeted cost containment for postarrest interventions may reduce the finance burden, there is an increasing need for funding research into prediction and prevention of cardiac arrest, which offers greater societal benefit.

Several conducting channels of ventricular tachycardia (VT) can be identified using voltage limit adjustment (VLA) of substrate mapping. However, the sensitivity or specificity to predict a VT isthmus is not high by using VLA alone. This study aimed to evaluate the efficacy of the combined use of VLA and fast-Fourier transform analysis to predict VT isthmuses.

Methods and Results:

VLA and fast-Fourier transform analyses of local ventricular bipolar electrograms during sinus rhythm were performed in 9 postinfarction patients who underwent catheter ablation for a total of 13 monomorphic VTs. Relatively higher voltage areas on an electroanatomical map were defined as high voltage channels (HVCs), and relatively higher fast-Fourier transform areas were defined as high-frequency channels (HFCs). HVCs were classified into full or partial HVCs (the entire or >30% of HVC can be detectable, respectively). Twelve full HVCs were identified in 7 of 9 patients. HFCs were located on 7 of 12 full HVCs. Five VT isthmuses (71%) were included in the 7 full HVC+/HFC+ sites, whereas no VT isthmus was found in the 5 full HVC+/HFC– sites. HFCs were identical to 9 of 16 partial HVCs. Eight VT isthmuses (89%) were included in the 9 partial HVC+/HFC+ sites, whereas no VT isthmus was found in the 7 partial HVC+/HFC– sites. All HVC+/HFC+ sites predicted VT isthmus with a sensitivity of 100% and a specificity of 80%.

Conclusions:

Combined use of VLA and fast-Fourier transform analysis may be a useful method to detect VT isthmuses.

Atrial fibrillation recurrence after initial long-term success of catheter ablation has been described, yet not well studied. We assessed the electrophysiological findings and outcomes of repeat ablation procedures in this setting.

Methods and Results:

Between 2000 and 2015, 10 378 patients underwent atrial fibrillation ablation and were enrolled in a prospectively maintained data registry. From this registry, we included all 137 consecutive patients who had initial long-term success, defined as freedom from recurrent arrhythmia for >36 months off antiarrhythmics, then underwent repeat ablation for recurrent atrial fibrillation. The median arrhythmia-free period that defined long-term success was 52 months (41–68 months). In redo ablations, reconnection along at least one of the pulmonary veins (PVs) was found in 111 (81%) patients. Reconnection along a left superior, left inferior, right superior, and right inferior PV was found in 64%, 62%, 50%, and 54% of patients, respectively, and were reisolated. Additional non-PV ablations were performed in 127 (92.7%) patients: posterior wall (46%), septal to right PVs (49%), superior vena cava (35%), roof lines (52%), and cavotricuspid isthmus (33%). After a median follow-up of 17 months (5–36.9 months), 103 patients (75%) were arrhythmia free (79 off antiarrhythmics, 24 on antiarrhythmics).

Conclusions:

PV reconnection is the most common electrophysiological finding in patients with atrial fibrillation recurrence after long-term success, but with lower rates than what had been reported for early recurrences. In our experience, repeat ablations in this setting involve complex ablation approaches to reisolate the PVs and modify the atrial substrate and are associated with good success rates.

Long-QT syndrome (LQTS), an inherited cardiac repolarization disorder, is an important cause of fetal and neonatal mortality. Detecting LQTS prenatally is challenging. A fetal heart rate (FHR) less than third percentile for gestational age is specific for LQTS, but the sensitivity is only 50%. Left ventricular isovolumetric relaxation time (LVIRT) was evaluated as a potential diagnostic marker for fetal LQTS.

Methods and Results:

LV isovolumetric contraction time, LV ejection time, LVIRT, cycle length, and FHR were measured using pulsed Doppler waveforms in fetuses. Time intervals were expressed as percentages of cycle length, and the LV myocardial performance index was calculated. Single measurements were stratified by gestational age and compared between LQTS fetuses and controls. Receiver-operator curves were performed for FHR and normalized LVIRT (N-LVIRT). A linear mixed-effect model including multiple measurements was used to analyze trends in FHR, N-LVIRT, and LV myocardial performance index. There were 33 LQTS fetuses and 469 controls included. In LQTS fetuses, the LVIRT was prolonged in all gestational age groups (P<0.001), as was the N-LVIRT. The best cutoff to diagnose LQTS was N-LVIRT ≥11.3 at ≤20 weeks (92% sensitivity, 70% specificity). Simultaneous analysis of N-LVIRT and FHR improved the sensitivity and specificity for LQTS (area under the curve=0.96; 95% confidence interval, 0.82–1.00 at 21–30 weeks). N-LVIRT, LV myocardial performance index, and FHR trends differed significantly between LQTS fetuses and controls through gestation.

Conclusions:

The LVIRT is prolonged in LQTS fetuses. Findings of a prolonged N-LVIRT and sinus bradycardia can improve the prenatal detection of fetal LQTS.

Cohort of 486 high-risk HCM patients with ICDs was assembled from 8 international centers. Clinical course and device interventions were addressed, and survey questionnaires assessed patient anxiety level and psychological well-being related to ICD therapy. Of 486 patients, 94 (19%) experienced appropriate ICD interventions terminating ventricular tachycardia/ventricular fibrillation, 3.7% per year for primary prevention, over 6.4±4.7 years. Of 94 patients, 87 were asymptomatic or only mildly symptomatic at the time of appropriate ICD interventions; 74 of these 87 (85%) remained in classes I/II without significant change in clinical status over the subsequent 5.9±4.9 years (up to 22). Among the 94 patients, there was one sudden death (caused by device failure; 1.1%); 3 patients died from other HCM-related processes unrelated to arrhythmic risk (eg, end-stage heart failure). Post-ICD intervention, freedom from HCM mortality was 100%, 97%, and 92% at 1, 5, and 10 years, distinctly lower than in ischemic or nonischemic cardiomyopathy ICD trials. HCM patients with ICD interventions reported heightened anxiety in expectation of future shocks, but with intact general psychological well-being and quality of life.

Conclusions:

In HCM, unlike ischemic heart disease, prevention of sudden death with ICD therapy is unassociated with significant increase in cardiovascular morbidity or mortality, or transformation to heart failure deterioration. ICD therapy does not substantially impair overall psychological and physical well-being.

Coupling between the ablation catheter and myocardium is critical to resistively heat tissue with radiofrequency ablation. The objective of this study was to evaluate whether a novel local impedance (LI) measurement on an ablation catheter identifies catheter–tissue coupling and is predictive of lesion formation.

Methods and Results:

LI was studied in explanted hearts (n=10 swine) and in vivo (n=10; 50–70 kg swine) using an investigational electroanatomic mapping system that measures impedance from an ablation catheter with mini-electrodes incorporated in the distal electrode (Rhythmia and IntellaNav MiFi OI, Boston Scientific). Explanted tissue was placed in a warmed (37 °C) saline bath mounted on a scale, and LI was measured 15 mm away from tissue to 5 mm of catheter–tissue compression at multiple catheter angles. Lesions were created with 31 and 50 W for 5 to 45 seconds (n=90). During in vivo evaluation of LI, measurements of myocardium (n=90) and blood pool (n=30) were guided by intracardiac ultrasound while operators were blinded to LI data. Lesions were created with 31 and 50 W for 45 seconds in the ventricles (n=72). LI of myocardium (119.7 ) was significantly greater than that of blood pool (67.6 ; P<0.01). Models that incorporate LI drop (LI) to predict lesion size had better performance than models that incorporate force-time integral (R2=0.75 versus R2=0.54) and generator impedance drop (R2=0.82 versus R2=0.58). Steam pops displayed a significantly higher starting LI and larger LI compared with successful radiofrequency applications (P<0.01).

Conclusions:

LI recorded from miniature electrodes provides a valuable measure of catheter–tissue coupling, and LI is predictive of lesion formation during radiofrequency ablation.

The Lesion Index (LSI) is a proprietary algorithm from Abbott Medical combining contact force, radiofrequency application duration, and radiofrequency current. It can be displayed during ablation with the TactiCath contact force catheter. The LSI Index was designed to provide real-time lesion formation feedback and is hypothesized to estimate the lesion diameter.

Methods and Results:

Before ablation, animals underwent cardiac computed tomography to assess atrial tissue thickness. Ablation lines (n=2–3 per animal) were created in the right atrium of 7 Göttingen mini pigs with point lesions (25 W). Within each line of ablation, the catheter tip was moved a prescribed distance (D/mm) according to 1 of 3 strategies: D=LSI+0 mm; D=LSI+2 mm; or D=LSI+4 mm. Two weeks after ablation, serial sections of targeted atrial tissue were examined histologically to identify gaps in transmural ablation. LSI-guided lines had a lower incidence of histological gaps (4 gaps in 69 catheter moves, 5.8%) than LSI+2 mm lines (7 gaps in 33 catheter moves, 21.2%) and LSI+4 mm lines (15 gaps in 23 catheter moves, 65.2%, P<0.05 versus D=LSI). LSI was calculated retrospectively as the distance between 2 adjacent lesions above the mean LSI of the 2 lesions. LSI values of ≤1.5 were associated with no gaps in transmural ablation.

Conclusions:

In this model of chronic atrial ablation, delivery of uninterrupted transmural linear lesions may be facilitated by using LSI to guide catheter movement. When LSI between adjacent lesions is ≤1.5 mm, no gaps in atrial linear lesions should be expected.

Implantable cardioverter defibrillator arrhythmia discrimination algorithms often are unable to discriminate ventricular from supraventricular arrhythmias. We sought to evaluate whether the response to antitachycardia pacing (ATP) in patients with an implantable cardioverter defibrillator could further discriminate ventricular from supraventricular arrhythmias in patients receiving ATP.

Methods and Results:

All episodes of ventricular or supraventricular tachycardia where ATP was delivered in patients enrolled in RAFT (Cardiac-Resynchronization Therapy for Mild-to-Moderate Heart Failure Trial) were included. RAFT randomized 1798 patients with New York Heart Association class II/III heart failure, left ventricular ejection fraction ≤30%, and QRS duration of ≥120 ms to a implantable cardioverter defibrillator±cardiac resynchronization therapy. The tachycardia cycle lengths (TCLs) before and after the delivery of ATP and the postpacing intervals were assessed. Overall, 10 916 ATP attempts were reviewed for 8150 tachycardia episodes in 924 patients. After excluding tachycardias where ATP terminated the episode or where the specific mechanism of the tachycardia was uncertain, we analyzed 3676 ATP attempts delivered for 2046 tachycardia episodes in 541 patients. A shorter difference between postpacing interval and TCL (PPI–TCL) was more likely to be associated with ventricular tachycardia than with supraventricular tachyarrhythmia (138.1±104.2 versus 277.4±126.9 ms; p<0.001). Analysis of the receiver operator curve for the PPI–TCL revealed an area under the curve of 0.803 (p<0.001; 95% confidence interval, 0.784–0.822). The majority of tachycardias with a PPI–TCL >360 ms were supraventricular with a PPI–TCL value of ≤360 ms having a sensitivity of 97.4% and specificity of 28.3% for ventricular tachycardia.

Conclusions:

The ATP response, specifically the PPI–TCL, can further discriminate ventricular from supraventricular arrhythmias in patients with implantable cardioverter defibrillators when the currently available discriminators fail.

The success of cryoablation of the pulmonary vein isolation (PVI) is dependent on transmural and circumferential ice formation. We hypothesize that rising impedance recorded from a ring electrode placed 2 mm from the cryoballoon signifies ice formation covering the balloon surface and indicates ice expansion. The impedance level enables titration of the cryoapplication time to avoid extracardiac damage while ensuring PVI.

Methods and Results:

In 12 canines, a total of 57 pulmonary veins were targeted for isolation. Two cryoapplications were delivered per vein with a minimum of 90 and maximum of 180-second duration. Cryoapplication was terminated on reaching a 500 change from baseline. Animals recovered 38±6 days post-procedure, and veins were assessed electrically for isolation. Heart tissue was histologically analyzed. Extracardiac structures were examined for damage. PVI was achieved in 100% of the veins if the impedance reached 500 in <90 seconds with freeze time of 90 seconds. When 500 was reached >90 to 180 seconds (142.60±29.3 seconds), 90% PVI was achieved. When the final impedance was between 200 and 500 with 180 seconds of freeze time, PVI was achieved in 86.8%. For impedance of <200 , PVI was achieved in 14%. No extracardiac damage was recorded.

Conclusions:

Impedance rise of 500 at <90 seconds with freeze time of 90 seconds resulted in 100% PVI. Impedance measurements from the nose of the balloon is a direct measure of ice formation on the balloon. It provides real-time feedback on the quality of the ablation and defines the cryoapplication termination time based on ice formation, limiting ice expansion to extracardiac tissues.

The aim of this study was to investigate whether the combination of QRS duration ≥120 ms (wide QRS duration [wQRS]) and late gadolinium enhancement (LGE) is a precise prognostic indicator for dilated cardiomyopathy.

Methods and Results:

We investigated the association between the combination of LGE plus wQRS and the primary end point (all-cause death) and a composite of sudden cardiac death (SCD) or aborted SCD in 531 patients with dilated cardiomyopathy. We also analyzed the association between the combination of LGE and wQRS and these end points among patients with a class I indication for implantable cardioverter defibrillator implantation. We divided study patients into 3 groups according to LGE status and QRS duration: 2 negative indices (LGE negative and narrow QRS), 1 positive index (LGE positive or wQRS), or 2 positive indices (LGE positive and wQRS), and followed them for 3.8 years. Multivariable Cox regression analysis identified 2 positive indices as a significant predictor of all-cause death (hazard ratio, 4.29 [1.19–15.47]; P=0.026). Among 317 patients with a class I indication for implantable cardioverter defibrillator, the 5-year event rate of SCD or aborted SCD was the lowest in the 2 negative indices group (1.4%). With propensity score–matching cohorts, the 2 negative indices group had a significantly lower event rate of SCD or aborted SCD than the other 2 groups (hazard ratio, 0.12 [0.01–0.97]; P=0.046).

Conclusions:

The combination of LGE and wQRS provides additional prognostic stratification compared with LGE status alone and might improve the appropriate use of implantable cardioverter defibrillator therapy in patients with dilated cardiomyopathy.

Despite the clear association between atrial fibrillation and risk for thromboembolic events (TEs), the clinical significance of new-onset device-detected atrial tachyarrhythmia (DDAT) and TE remains disputed. We aimed to determine the risk of TE in patients with new-onset DDAT.

New-onset DDAT is common, affecting close to one quarter of all patients with implanted pacemakers or defibrillators. Adjudication of atrial electrograms further identifies at-risk patients, even when relatively short detection thresholds are used.

Four hundred thirty patients (215 male, 55.4±22.1 years) with indication to electrophysiological study or ablation of supraventricular tachycardias were enrolled. All participating physicians agreed to follow the as low as reasonably achievable policy. A procedure was defined as ZFL when no fluoroscopy was used. The total fluoroscopy time inversely correlated to the number of procedures previously performed by each operator since study start (r=–0.112; P=0.02). Two hundred eighty-nine procedures (67.2%) were ZFL; multivariable analysis identified as predictors of ZFL: procedure after the 30th for each operator, compared with procedures up to the ninth (P=0.011; hazard ratio, 3.49; 95% confidence interval [CI], 1.79–6.80); the type of arrhythmia (P=0.031; electrophysiological study and atrioventricular nodal reentry tachycardia ablation having the highest probability of ZFL; hazard ratio, 6.87; 95% CI, 2.08–22.7 and hazard ratio, 2.02; 95% CI, 1.04–3.91, respectively); the operator’s (P=0.002) and patient’s age (P=0.009). Among operators, achievement of ZFL varied from 0% to 100%; 8 (22.8%) operators achieved ZFL in <25% of their procedures; 17 (48.6%) operators achieved ZFL in >75% of their procedures. The probability of ZFL increased by 2.8% (hazard ratio, 0.98; 95% CI, 0.97–0.99) as patient’s age decreased by 1 year. Acute procedural success was obtained in all cases.

Conclusions:

The use of 3-dimensional mapping system completely avoided the use of fluoroscopy in most cases, with very low fluoroscopy time in the remaining and high safety and effectiveness profiles. Achievement of ZFL was predicted by the type of arrhythmia, operator’s experience, and patient’s age.

From May 2013 to September 2015, 218 PVSs were performed 6 days (5–7) after ablation (186 noninvasive programmed stimulations and 32 invasive PVS) in 210 consecutive patients (ischemic, 48%; median left ventricular ejection fraction, 37%; syncope, 35% with trauma associated 6%), while patients were awake and under β-blocker therapy. After ablation, implantable cardioverter defibrillators were programmed according to noninvasive programmed stimulations results (class A—noninducible; class B—nondocumented inducible VT; and class C—documented inducible VT), with high and delayed VT detection intervals. Concordance between PVS end procedure and PVS day 6 was 67%. Positive predictive value and negative predictive value were higher for PVS day 6 (53% and 88% versus 43% and 71%). Ischemic and patients with preserved ejection fraction showed the highest negative predictive value (91% and 96%). Among 46 of 174 (26%) noninducible patients at PVS end procedure, but inducible at day 6, 59% had VT recurrence at 1-year follow-up; recurrences were 9% when both studies were noninducible. There were no inappropriate shocks; incidence of syncope was 3%; and none was harmful. The rate of appropriate shocks per patient per month according to noninvasive programmed stimulations results was significantly reduced, comparing the month before and after ablation (class A: 2 [0.75–4] versus 0; class B: 2 [1–4] versus 0; class C: 2 [1–4] versus 0; P<0.001).

Conclusions:

PVS at day 6 predicts VT recurrence more accurately allowing to identify patients who might benefit from a redo ablation and addressing implantable cardioverter defibrillator programming.

This study investigated the prevalence, electrocardiographic and electrophysiological characteristics, and ablation outcome of idiopathic ventricular arrhythmias (VAs) originating from the infundibular muscles (IFMs) in the right ventricle consisting of the parietal band (PB) and septal band (SB).

Methods and Results:

We studied 19 patients with idiopathic VA origins in the PB in 14 and SB in 5 among 294 consecutive patients with VA origins in the right ventricle. PB and SB VAs exhibited left bundle branch block with a left inferior (n=12) or superior (n=2) axis and left (n=4) or right inferior (n=1) axis pattern, respectively. In lead I, all PB VAs exhibited R waves while SB VAs often exhibited S waves. A QS pattern in lead aVR and the presence of a notch in the mid-QRS were common in all IFMs VAs. During IFMs VAs, a far-field ventricular electrogram with an early activation was always recorded in the His bundle region regardless of the location of the VA origins. With 9.2±6.9 radiofrequency applications and a duration of 972±946 seconds, catheter ablation was successful in 15 patients. VAs recurred in 4 during a follow-up period of 43±24 months. A change in the QRS morphology was observed spontaneously in 5 patients, immediately after ablation in 4, and at the time of the VA recurrence in 2.

Conclusions:

Idiopathic VAs originating from the IFMs are rare (PB>SB). Catheter ablation of these IFMs VAs was challenging, requiring a large amount of the radiofrequency energy delivery for a successful ablation with a relatively high recurrence rate.

Clinical outcomes after ablation of persistent atrial fibrillation remain suboptimal. Identification of AF drivers using a novel integrated mapping technique may be crucial to ameliorate the clinical outcome.

Methods and Results:

Persistent AF patients were prospectively enrolled to undergo high-density electrophysiological mapping to identify repetitive-regular activities (RRas) before modified circumferential pulmonary vein (PV) ablation. They have been randomly assigned (1:1 ratio) to ablation of RRa followed by modified circumferential PV ablation (mapping group; n=41) or modified circumferential PV ablation alone (control group; n=40). The primary end point was freedom from arrhythmic recurrences at 1 year. In total, 81 persistent AF patients (74% male; mean age, 61.7±10.6 years) underwent mapping/ablation procedure. The regions exhibiting RRa were 479 in 81 patients (5.9±2.4 RRa per patient): 232 regions in the mapping group (n=41) and 247 in the control group (n=40). Overall, 185 of 479 (39%) RRas were identified within the PVs, whereas 294 of 479 (61%) in non-PV regions. Mapping-guided ablation resulted in higher arrhythmia termination rate when compared with conventional strategy (25/41, 61% versus 12/40, 30%; P<0.007). Total radiofrequency duration (P=0.38), mapping (P=0.46), and fluoroscopy times (P=0.69) were not significantly different between the groups. No major procedure-related adverse events occurred. After 1 year, 73.2% of mapping group patients were free from recurrences versus 50% of control group (P=0.03).

Conclusions:

Targeted ablation of regions showing RRa provided an adjunctive benefit in terms of arrhythmia freedom at 1-year follow-up in the treatment of persistent AF. These findings might support a patient-tailored strategy in subjects with nonparoxysmal AF and should be confirmed by additional larger, randomized, multicenter studies.

Immunohistochemistry studies suggest that the anatomic substrate of the slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT) is the left inferior nodal extension. We hypothesized that slow pathway ablation from the left septum is an effective alternative to right-sided ablation.

Methods and Results:

We analyzed our databases of AVNRT in search of cases that had used slow pathway ablation from the left septum because of failure of right septal ablation, and then prospectively subjected consenting patients to a left septal–only procedure. Of 1342 patients subjected to right septal slow pathway ablation for AVNRT, 15 patients, 11 with typical and 4 with atypical AVNRT, had a left septal approach after unsuccessful right-sided ablation (R+L group). Eleven patients were subjected to a left septal–only approach for slow pathway ablation without a previous right septal attempt (L group). Fluoroscopy times in the R+L and L groups were 30.5 (21.0–44.0) and 20.0 (17.0–25.0) minutes, respectively (P=0.061), and radiofrequency current delivery times were 11.3 (5.0–19.1) and 10.0 (7.0–12.0) minutes, respectively (P=0.897). There was no need for additional ablation lesions at other anatomic sites in either group, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia for the R+L and L groups were 6.7% and 0%, respectively, in the 3 months after ablation (P=1.000).

Conclusions:

Left septal ablation at the anatomic site of the left inferior nodal extension is an alternative for ablation of both typical and atypical AVNRT when ablation at the right posterior septum is ineffective.

Previous studies indicated the importance of the intrinsic left ventricular (LV) electric delay (QLV) for optimal benefit to cardiac resynchronization therapy. We investigated the use of QLV for achieving optimal acute hemodynamic response to cardiac resynchronization therapy with a quadripolar LV lead.

Methods and Results:

Forty-eight heart failure patients with a left bundle branch block were prospectively enrolled (31 men; age, 66±10 years; LV ejection fraction, 28±8%; QRS duration, 176±14 ms). Immediately after cardiac resynchronization therapy implantation, invasive LV pressure–volume loops were recorded during biventricular pacing with each separate electrode at 4 atrioventricular delays. Acute cardiac resynchronization therapy response, measured as change in stroke work (%SW) compared with intrinsic conduction, was related to intrinsic interval between Q on the ECG and LV sensing delay (QLV), normalized for QRS duration (QLV/QRSd), and electrode position. QLV/QRSd was 84±9% and variation between the 4 electrodes 9±5%. %SW was 89±64% and varied by 39±36% between the electrodes. In univariate analysis, an anterolateral or lateral electrode position and a high QLV/QRSd had a significant association with a large %SW (all P <0.01). In a combined model, only QLV/QRSd remained significantly associated with %SW (P<0.05). However, a direct relation between QLV/QRSd and %SW was only seen in 24 patients, whereas 24 patients showed an inverse relation.

Conclusions:

The large variation in acute hemodynamic response indicates that the choice of the stimulated electrode on a quadripolar lead is important. Although QLV/QRSd was associated with acute hemodynamic response at group level, it cannot be used to select the optimal electrode in the individual patient.

Current guidelines recommend implantable cardioverter-defibrillator (ICD) therapy in survivors of sudden cardiac arrest (SCA), except in those with completely reversible causes. We sought to examine the impact of ICD therapy on mortality in survivors of SCA associated with reversible causes.

Methods and Results:

We evaluated the records of 1433 patients managed at our institution between 2000 and 2012 who were discharged alive after SCA. A reversible and correctable cause was identified in 792 (55%) patients. Reversible SCA cause was defined as significant electrolyte or metabolic abnormality, evidence of acute myocardial infarction or ischemia, recent initiation of antiarrhythmic drug or illicit drug use, or other reversible circumstances. Of the 792 SCA survivors because of a reversible and correctable cause (age 61±15 years, 40% women), 207 (26%) patients received an ICD after their index SCA. During a mean follow-up of 3.8±3.1 years, 319 (40%) patients died. ICD implantation was highly associated with lower all-cause mortality (P<0.001) even after correcting for unbalanced baseline characteristics (P<0.001). In subgroup analyses, only patients whose SCA was not associated with myocardial infarction extracted benefit from ICD (P<0.001).

Conclusions:

In survivors of SCA because of a reversible and correctable cause, ICD therapy is associated with lower all-cause mortality except if the SCA was because of myocardial infarction. These data deserve further investigation in a prospective multicenter randomized controlled trial, as they may have important and immediate clinical implications.

Transvenous lead extraction is an integral part of management of patients with cardiovascular implantable electronic devices. Real-world incidence and predictors of perioperative complications in extractions involving implantable cardioverter-defibrillator leads have not been described in detail.

Methods and Results:

Data from the National Cardiovascular Data Registry Implantable Cardioverter-Defibrillator Registry were analyzed. Lead extraction was defined as removal of leads implanted for >1 year. Predictors of major perioperative complications for all extraction procedures (11 304) and for high-voltage lead (8362, 74%), across 762 centers, were analyzed using univariate and multivariate logistic regression. Major complication occurred in 258 (2.3%) extraction procedures. Of these 258 with a complication, 41 (16%) required urgent cardiac surgery. Of these 41, 14 (34%) died during surgery. Among the total 98 (0.9%) deaths reported, 18 (0.16% of total) occurred during transvenous lead extraction. In multivariable logistic regression analysis, female sex, admission other than electively for procedure, ≥3 leads extracted, longer implant duration, dislodgement of other leads, and patient’s clinical status requiring lead extraction (infection/perforation) were associated with increased risk of complications. Smaller lead diameter, flat versus round coil shape, and greater proximal surface coil area were multivariate predictors of major perioperative complications specific to high-voltage leads.

Conclusions:

The rate of major complications and mortality with transvenous lead extraction is similar in the real-world outcomes to that reported in recent single-center studies from high-volume centers. There is significant risk of urgent cardiac surgery, which carries a high mortality, and planning for appropriate cardiothoracic surgery backup is imperative.

Pulmonary vein isolation (PVI) is effective for maintenance of sinus rhythm in 50% to 75% of patients with paroxysmal atrial fibrillation, and it is not uncommon for patients to require additional ablation after PVI. We prospectively evaluated the relative effectiveness of 2 post-PVI ablation strategies in paroxysmal atrial fibrillation.

Methods and Results:

A total of 500 patients (mean age, 55.7±11.0 years; 74.6% male) were randomly assigned to undergo ablation by 2 different strategies after PVI: (1) elimination of non-PV triggers (group A, n=250) or (2) stepwise substrate modification including complex fractionated atrial electrogram or linear ablation until noninducibility of atrial tachyarrhythmia was achieved (group B, n=250). During a median follow-up of 26.0 months, 75 (32.2%) patients experienced at least 1 episode of recurrent atrial tachyarrhythmia after the single procedure in group A compared with 105 (43.8%) patients in group B (P value in log-rank test of Kaplan–Meier analysis: 0.012). Competing risk analysis showed that the cumulative incidence of atrial tachycardia was significantly higher in group B compared with group A (P=0.007). With the exception of total ablation time, there were no significant differences in fluoroscopic time or procedure-related complications between the 2 groups.

Conclusions:

Elimination of triggers as an end point of ablation in patients with paroxysmal atrial fibrillation decreased long-term recurrence of atrial tachyarrhythmia compared with a noninducibility approach achieved by additional empirical ablation. The post-PVI trigger test is thus a better end point of ablation for paroxysmal atrial fibrillation.

Circumferential pulmonary vein isolation (CPVI) is increasingly performed for the treatment of symptomatic drug-refractory paroxysmal atrial fibrillation. Long-term data for >10 years after CPVI are sparse. We investigated the long-term clinical outcome and progression of paroxysmal atrial fibrillation after double-lasso and 3-dimensional electroanatomical mapping–guided CPVI.

Ten-year single-procedural outcome of CPVI in patients with paroxysmal atrial fibrillation resulted in stable sinus rhythm in 32.9% and in 62.7% of patients after multiple procedures. The progression rate to persistent AF was remarkably low.

Safety and feasibility data on transvenous lead extraction (TLE) in the challenging population of adults with congenital heart disease (A-CHD) are limited. Herein, we report the results of TLE in A-CHD during a 20-year period.

Methods and Results:

All consecutive TLE procedures in A-CHD were included in a monocentric prospective registry from 1996. A total of 121 leads were extracted in 49 A-CHD (median age, 38 years; 51% men) during 71 TLE procedures. Twenty-four (49%) patients had transposition of the great arteries. Main indications for extraction were infection in 34 (48%) and lead failure in 22 (31%). A laser sheath was required for 56 (46%) leads and a femoral approach for 10 (8%). Complete TLE was achieved for 111 leads (92%). In multivariable analysis, lead duration (odds ratio, 1.02; 95% confidence interval, 1.00–1.04; P<0.01) and number of previous cardiac surgeries (odds ratio, 2.65; 95% confidence interval, 1.52–4.67; P<0.01) were predictive of TLE failure. No perioperative death or pericardial effusion was observed. Subpulmonary atrioventricular valve regurgitation increased in 8 patients (5 with transposition of the great arteries) and was independently associated with an implantable cardioverter defibrillator lead (odds ratio, 9.69; 95% confidence interval, 1.31–71.64; P=0.03) and valvular vegetation (odds ratio, 7.29; 95% confidence interval, 1.32–40.51; P=0.02). After a median of 54 (19–134) months of follow-up after the first TLE, 3 deaths occurred independently from lead management.

Conclusions:

Despite complex anatomic issues, TLE can be achieved successfully in most A-CHD using advanced extraction techniques. Subpulmonary atrioventricular valve regurgitation is a prevalent complication, particularly in patients with transposition of the great arteries.

Biatrial tachycardia (BiAT) is a rare form of atrial macroreentrant tachycardia, in which both atria form a critical part of the circuit. We aimed to identify the characteristics and precise circuits of single-loop macroreentrant BiATs.

Methods and Results:

We identified 8 patients (median age, 59.5 years old) with 9 BiATs in a cohort of 336 consecutive patients from 2 institutions who had undergone AT catheter ablation using an automatic ultrahigh-resolution mapping system. Seven of the 8 patients had a history of persistent AF ablation, including septal or anterior left atrium ablation before developing BiAT. One of the 8 patients had a history of an atrial septal patch closure with a massively enlarged right atrium. Nine ATs (median cycle length, 334 ms; median 12 561 points in the left atrium; 8814 points in the right atrium) were diagnosed as single-loop macroreentrant BiATs. We observed 3 types of BiAT (1) BiAT with a perimitral and peritricuspid reentrant circuit (n=3), (2) BiAT using the right atrium septum and a perimitral circuit (n=3), and (3) BiAT using only the left atrium and right atrium septum (n=3). Catheter ablation successfully terminated 8 of the 9 BiATs.

Conclusions:

All patients who developed BiAT had an electric obstacle on the anteroseptal left atrium, primarily from prior ablation lesions. In this situation, mapping of both atria should be considered during AT. Because 3 types of single-loop BiAT were observed, ablation strategies should be adjusted to the type of BiAT circuit.

Ventricular arrhythmias are a feared complication of arrhythmogenic right ventricular dysplasia/cardiomyopathy. In 2015, an International Task Force Consensus Statement proposed a risk stratification algorithm for implantable cardioverter-defibrillator placement in arrhythmogenic right ventricular dysplasia/cardiomyopathy.

While the algorithm differentiates arrhythmic risk well overall, it did not distinguish ventricular fibrillation/flutter risks of patients with Class I and IIa implantable cardioverter-defibrillator indications. Limited differentiation was seen for primary prevention cases. As these are vital uncertainties in clinical decision-making, refinements to the algorithm are suggested prior to implementation.

Long-term results of substrate modification for ablation of ventricular tachycardia (VT) have not been reported. We report long-term outcomes of substrate elimination targeting local abnormal ventricular activities (LAVA) for post–myocardial infarction VT.

Methods and Results:

One hundred fifty-nine consecutive patients undergoing first ablation were included (65±11 years, 92% implantable cardioverter defibrillators, 54% storms, and 73% appropriate shocks). LAVA were identified in 92% and VT was inducible in 73%. Complete LAVA elimination and noninducibility after ablation were achieved in 64% and 85%. During a median follow-up of 47 months (interquartile range, 34–82), single-procedure ventricular arrhythmia (VA)–free survival was 55% (10% storms and 19% shocks). The VA-free survival was 73%, 68%, 61%, 55%, and 49% after 1, 2, 3, 4, and 5 years, respectively. Complete LAVA elimination was associated with improved outcomes: VA-free survival of 82% at 1 year and 61% at 5 years. In the subgroup treated with multielectrode mapping and real-time image integration, VA-free survival was 86% and 65% at 1 year and 4 years, respectively. Including repeat procedures in 18% of pts (1.3±0.6 ablations/pt) outcomes improved to 69% VA-free survival (2% storms and 9% shocks) during median 46-month follow-up. Overall survival was 91% at 1 year and 77% at 5 years of follow-up.

Conclusions:

In this monocentric study, substrate modification targeting LAVA for post–myocardial infarction VT resulted in a substantial reduction of VT storm and implantable cardioverter defibrillator shocks and up to 49% of patients free from arrhythmia at 5 years after a single procedure. Complete LAVA elimination, multielectrode mapping, and real-time integration were associated with improved VA-free survival.

Catheter ablation for atrial fibrillation has potential to cause esophageal thermal injury. Esophageal temperature monitoring during ablation is commonly used; however, it has not eliminated thermal injuries, possibly because conventional sensors have poor spatial sampling and response characteristics. To enhance understanding of temperature dynamics that may underlie esophageal injury, we tested a high-resolution, intrabody, infrared thermography catheter to continuously image esophageal temperatures during ablation.

Methods and Results:

Atrial fibrillation ablation patients were instrumented with a flexible, 9F infrared temperature catheter inserted nasally (n=8) or orally (n=8) into the esophagus adjacent to the left atrium. Ablation was performed while the infrared catheter continuously recorded surface temperatures from 7680 points per second circumferentially over a 6-cm length of esophagus. Physicians were blinded to temperature data. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that most patients (10/16) experienced ≥1 events where peak esophageal temperature was >40°C. Three patients experienced temperatures >50°C; and 1 experienced >60°C. Analysis of temperature data for each subject’s maximum thermal event revealed high gradients (2.3±1.4°C/mm) and rates of change (1.5±1.3°C/s) with an average length of esophageal involvement of 11.0±5.4 mm. Endoscopy identified 3 distinct thermal lesions, all in patients with temperatures >50°C; all resolved within 2 weeks.

Conclusions:

Infrared thermography provided dynamic, high-resolution mapping of esophageal temperatures during cardiac ablation. Esophageal thermal injury occurred with temperatures >50°C and was associated with large spatiotemporal gradients. Additional studies are warranted to determine the relationships between thermal parameters and esophageal injury.

Until today, catheter interventional mapping and ablation of atrial fibrillation (AF) has been limited to the right and left atrial endocardium. We report feasibility, electrophysiological findings, and clinical outcome using a combined endo-/epicardial catheter approach for mapping and ablation of AF.

Methods and Results:

Fifty-nine patients with permanence of pulmonary vein isolation and further symptomatic recurrences of paroxysmal AF, persistent AF, or atrial tachycardia underwent reablation using biatrial endo-/epicardial mapping and ablation. Identification of arrhythmia substrates and selection of ablation strategy were based on sinus rhythm voltage mapping. Using continuous monitoring and a 3-month blanking period, freedom from AF/atrial tachycardia ≥2 minutes was defined as primary end point. In all patients, endo-/epicardial mapping and ablation was feasible using standard technologies of catheter access, 3-dimensional mapping, and radiofrequency ablation. Epicardial mapping and ablation did not add procedural risks. Exclusively epicardial low voltage substrates were found in 14% of the patients. For the first time, novel epicardial conduction abnormalities located in the epicardial fiber network were described in human AF patients (19% of the cohort). Epicardial ablation was needed in 80% of the patients. Over 23±10 months of follow-up freedom from arrhythmia recurrences measured 73%.

Conclusions:

Catheter-based endo-/epicardial mapping and ablation of AF was feasible and safe. Epicardial mapping provided new insights into AF mechanisms. Epicardial ablation increased transmurality of ablation lesions. Clinical outcome in this cohort of complex AF patients was favorable, indicating potential further development of current AF treatment.

We developed a novel electrocardiographic marker, T-wave area dispersion (TW-Ad), which measures repolarization heterogeneity by assessing interlead T-wave areas during a single cardiac cycle and tested whether it can identify patients at risk for sudden cardiac death (SCD) in the general population.

We measured the major K+ currents (IKr, IKs, and IK1) and their Ca2+- and β-adrenergic dependence in rabbit ventricular myocytes in chronic pressure/volume overload–induced HF (versus age-matched controls). APD was significantly prolonged only at lower pacing rates (0.2–1 Hz) in HF under physiological ionic conditions and temperature. However, when cytosolic Ca2+ was buffered, APD prolongation in HF was also significant at higher pacing rates. Beat-to-beat variability of APD was also significantly increased in HF. Both IKr and IKs were significantly upregulated in HF under action potential clamp, but only when cytosolic Ca2+ was not buffered. CaMKII (Ca2+/calmodulin-dependent protein kinase II) inhibition abolished IKs upregulation in HF, but it did not affect IKr. IKs response to β-adrenergic stimulation was also significantly diminished in HF. IK1 was also decreased in HF regardless of Ca2+ buffering, CaMKII inhibition, or β-adrenergic stimulation.